Photoacoustic endoscopy

Abstract

We have developed photoacoustic endoscopy with a miniaturized imaging probe. A light-guiding optical fiber, an ultrasonic sensor, and a mechanical scanning unit are integrated to enable circumferential sector scanning, which produces B-scan images. Biological tissues, including the gastrointestinal tract of a rat, have been imaged ex vivo or in situ.

Figures

Fig. 1

(a) Schematic of the photoacoustic endoscopic probe. GM, geared micromotor; JB, jewel bearings; MN, magnets; OF, optical fiber; PM, plastic membrane (imaging window); SM, scanning mirror; UST, ultrasonic transducer. (b) Photograph of the probe. (c) Field of view. SW, stainless steel wall (blocked zone: 110°); PM, plastic membrane (imaging zone: 250°).

Fig. 2

(a) Typical photoacoustic (PA) A-line of the carbon fiber: raw data and amplitude of the Hilbert-transform. (b) Transverse PSF for the carbon fiber. (c) Photoacoustic image of a carbon fiber (6 μm in diameter): Cartesian coordinate representation. (d) Polar coordinate representation of image (c). (e) SNR vs. target distance. (f) Radial resolution vs. target distance. (g) Transverse resolution vs. target distance.

Fig. 3

(a) Photograph of the rat's abdominal surface. (b) Photoacoustic (PA) B-scan image of the tissue shown in (a). (c) Photograph of the rat's abdominal tissue segment (inner surface). The inset shows the whole sample from the outside. (d) PA image of the tissue shown in (c). (e) Photograph of the intact large intestinal tract, into which the endoscope was inserted. (f) PA image of the tissue shown in (e) from inside the intestine. BV, blood vessel; LB, laser beam (570 nm). Yellow arrow: scanning direction and range.